The present invention relates to a chemical cell type of component sensor for detecting the concentration of a specific component contained in a metal melt and, more particularly, to a component sensor for high-temperature purposes, which uses a composite molten salt electrolyte consisting of a solid phase and a liquid phase. The term "metal melt" as used herein is understood to mean the melt of a metal or alloy.
In producing galvanized steel plates for industrial purposes, esp., automotive purposes by hot dip coating, a small amount of aluminum is being now generally added to zinc for improving their quality. A general purpose of adding aluminum is to improve the adhesion between the steel plates and zinc. In this galvanized steel plate production line, an aluminum mother alloy is fed into a molten zinc bath for hot dip coating to regulate the concentration of aluminum in the molten zinc bath. Then, the steel plate is coated with zinc by hot dip coating. In order to place post-steps under proper control, it is desired to provide a successive detection of the content of aluminum in the molten zinc bath, thereby achieving intermediate and proper automatic control of the concentration of aluminum in the molten zinc bath.
Conventional means for detecting the concentration of a specific component in this type of molten metal has involved sampling a part of the molten metal bath intermittently, solidifying it--followed by its dissolution in an acid to form an aqueous solution, and analyzing this aqueous solution by ordinary chemical analysis or atomic-absorption spectroscopy. It has been reported that, for scientific purposes, the activity (or concentration) of alloy components can be made electrochemically with a molten salt electrolyte--see "Acta Metallurgica", 2, pp. 621-631 (1954).
For such conventional techniques, however, it is required to sample out a part of the molten metal bath. This makes it impossible to make an in-situ measurement of the concentration of a particular component and so needs much labor and time to determine that concentration. Another problem is that difficulty is involved in reducing the regulation of component concentrations in the molten metal bath to automation. In other words, complicated analytical procedures are needed for determining the concentration of the particular component after a part of the metal melt has been sampled out, and a considerable length of time is required until the results of analysis are available. The above-mentioned report on measuring the activity of alloy components is directed to using a molten salt electrolyte rather than a solid electrolyte.
Having been accomplished to seek a solution to such problems, the present invention has for its object to provide a component sensor for molten metals, which can continuously detect the concentration of a particular component in a molten metal by electrical signals, can be used at relatively high temperatures, say, 420.degree.-800.degree. C. and has high resolving power in a wide concentration range.